Reset object rotation
The rotation which was done in Edit mode can't be reset as it would be possible with rotation in Object mode. Depending on the case, it's possible to use workaround.

Create an empty. While still in Object mode, enable Snap During Transform and choose Snap to Face as type of element. Enable Align Rotation With the Snapping Target button.

Grab empty, hovering the mouse over faces which should be rotated along world axes. I.e. in case of building this will be faces representing the floor.

Once empty is snapped, it gained new rotation values. Parent object to the empty with Ctrl+P.

Select empty and clear its rotation transforms (Alt+R). Object will follow changed rotation and should become aligned along world axes (or at least roughly aligned).

Clear Parent with (Alt+P) by selecting Clear and Keep Transformation.

Select empty, then delete with X.